Effect of specimen size and oxygen partial pressure on creep characteristics for mod. 9Cr-1Mo steel
Kanayama, Hideyuki; Hiyoshi, Noritake*; Ito, Takamoto*; Ogawa, Fumio*; Wakai, Takashi
This study presents creep characteristics of Mod. 9Cr-1Mo steel with various sized specimens and environment. Creep tests were performed using three different sizes of specimen and three different type of testing environment. Specimens are a bulk specimen which has 6mm diameter and 30mm gage length, a miniature specimen which has 2mm diameter and 10mm gage length and a thin plate specimen which has 0.76mm thickness, 1.5mm width and 7.62mm gage length. Three different type of testing environment are air, 99.99% Ar gas and vacuum. In the same environmental condition, there was no effect of specimen size on time to rupture. Time to rupture of Mod. 9Cr-1Mo steel in Ar gas was shorter than that in air and vacuum. Oxide thickness is not dominant factor in time to rupture. Fracture mode at specimen surface in Ar gas might be dominant factor in shorter time to rupture. Effect of specimen size and environment on creep strength of Mod. 9Cr-1Mo steel was evaluated on the basis of thinning.